Free vs paid doesn't have anything to do with the quality of the program (as most Cura vs S3D users will know). They all have their good and bad sides. Look at McAfee. It's so bad, the original creator wanted the name changed (since he is no longer associated with it).

Try putting it into TrendMicro as exclude ("Cura 3.1") the directory in lieu of exclude Cura the program.